The present invention relates to thermal insulation material and more particularly to insulation made from cellulosic fibers having high flame-retardant properties.
Fiberized wood or other fibrous cellulosic material serves as an excellent insulating material when blown into the walls, floors, or attic of a home or other type of building that must be protected against heat losses. Cellulosic insulating materials are light in weight and inexpensive. The R value per inch of such insulating material is quite high and in many cases may equal or exceed the R value per inch of fiberglass batting.
The use of fiberized wood or other cellulosic material as insulation is known in the art. For example, Heritage, U.S. Pat. No. 2,325,055, teaches forming a thermal insulation material by refining wood chips at elevated temperatures in the presence of steam. Various bonding, fire-proofing, and mold-preventing agents are added to the material prior to its entry into the refiner. Portz, U.S. Pat. No. 2,470,641, adds dry boric acid to disintegrated newsprint to form a fire-resistant insulating material.
However, there has been a reluctance in the past to use cellulosic insulating materials because of problems with insuring adequate fire resistance of the material. To meet stringent fire regulation standards the insulating material must not be ignitable in the presence of heat. Present federal regulations require cellulosic insulating material to have a critical radiant flux of at least 0.12 watts/cm.sup.2.
Accordingly, the need still exists in the art for a process of preparing wood or other cellulosic fiber insulating material which meets or exceeds the regulated fire resistance standards.